Three rounds of cold Arctic air from a shifting polar vortex are expected to plunge much of the central and eastern U.S. into a cold snap in the coming weeks, meteorologists say. The first wave of the triple whammy of winter weather is happening this week.

“The week will end with some of the coldest air of the season so far, as a front advances from the Midwest into the Northeast and mid-Atlantic,” said Renee Duff, AccuWeather senior meteorologist.

Meteorologists forecast two more blasts of frigid temperatures for millions of people over the next two weeks.

“A displacement of the polar vortex is allowing Arctic air to seep into the central and eastern U.S.,” Duff explained. “A second cold outbreak is in the forecast next week, and a third round of frigid air is likely during the middle of the month.”

When will the cold air arrive?

Brutally cold temperatures hit portions of the Midwest on Thursday morning, while the northern mid-Atlantic and New England will feel the freeze on Friday morning, according to the National Weather Service.

“The outbreak this week will be the first of probably three such rounds with it,” said AccuWeather’s lead long-range meteorologist, Paul Pastelok. “Another cold blast is likely next week and a third the week after that.”

How cold will it get?

“Low temperatures in the negative single digits and teens for the Midwest and single digits and teens for the northern Mid-Atlantic/New England may challenge several daily record low temperatures,” the NWS said.

Along the Interstate 95 Northeast corridor, meteorologists predict temperatures will plunge into the 10s and 20s as the cold air moves east. Subzero temperatures are expected from the Dakotas and Minnesota to Iowa and Nebraska due to the blast of Arctic air.

For the next couple of days, here are the general forecast temperature highs from the NWS:

• Midwest: teens to 20s

• New England: 20s and 30s

• Central/southern Plains east to the mid-Atlantic: 30s and 40s

• Texas and Southeast: 40s and 50s

What is a polar vortex?

Let’s start with the “polar” part. A large area of low pressure and cold air is always surrounding Earth’s north and south poles. “Vortex” refers to the counterclockwise direction of air that keeps the colder air near both poles. During wintertime in the northern hemisphere, it’s common for the polar vortex to expand, pushing the cold air from the north pole to the south along the jet stream, according to the NWS.

Staying safe if you lose power

AccuWeather advises people to complete winterizing their homes and water lines, and to have their furnaces checked and heating oil or propane ordered as soon as possible.

Here are some things the American Red Cross recommends if you lose power and your main heat source:

• Only use generators, grills and camp stoves that are placed outdoors and away from windows to prevent carbon monoxide poisoning.

• Never use a cooking oven or stove to heat your home, as this can lead to carbon monoxide poisoning and home fires.

• Use battery-powered lanterns or flashlights instead of candles due to the fire risk.

• Close off any rooms you don’t need.

• Use care when using fireplaces and space heaters. Keep anything that could catch fire at least 3 feet away from the heat source.

Staying safe if you have to go outdoors

The American Red Cross advises that if you must go outside, keep as much of your skin covered as possible to avoid frostbite. Wear layers of loose-fitting, warm clothing and a hat; mittens snug at the wrist are better than gloves. Wear a ski mask or a scarf to help cover your face, and water-resistant boots, if possible, to help keep your feet dry.

Avoid overexertion that often occurs from walking through deep snow; it could bring on a heart attack or a more serious medical condition.